Normal tissue homeostasis is a highly regulated process of cell proliferation and cell death. An imbalance of either cell proliferation or cell death can develop into a cancerous state. For example, cervical, kidney, lung, pancreatic, colorectal, and brain cancer are just a few examples of the many cancers that can result. In fact, the occurrence of cancer is so high that over 500,000 deaths per year are attributed to cancer in the United States alone.
Currently, there are few effective options for the treatment of common cancer types. The course of treatment for a given individual depends on the diagnosis, the stage to which the disease has developed and factors such as age, sex, and general health of the patient. The most conventional options of cancer treatment are surgery, radiation therapy and chemotherapy. Chemotherapy is associated with substantial toxicity that can negatively impact quality of life. Surgery plays a central role in the diagnosis and treatment of cancer. Typically, a surgical approach is required for biopsy and to remove cancerous growths. However, if the cancer has metastasized and is widespread, surgery is unlikely to result in a cure and an alternate approach must be taken. New agents and therapies are needed to extend life and improve quality of life in patients with cancer.
Replication-selective oncolytic viruses hold promise for the treatment of cancer. These viruses can cause tumor cell death through direct replication-dependent oncolytic effects. In addition, viruses are able to enhance the cell-mediated antitumoral immunity within the host. These viruses also can be engineered to express therapeutic transgenes within the tumor to enhance antitumoral efficacy. However, major limitations exist to this therapeutic approach as well.